To distribute air in an HVAC system, an air distribution system moves and conditions the air. An air-handling unit (AHU) includes heating coils, cooling coils, and fans for mixing outside air, heating or cooling the air, and moving the air to zones, rooms, or other areas local to the occupant space. Terminal units in the zones, rooms, or other areas local to the occupant space also include heating coils, cooling coils, and fans for further heating or cooling the air and outputting the air to the occupant space.
HVAC systems consume significant energy. The amount of energy used depends on the operating state of the system, which includes the operating states of the AHU and terminal units. One optimization technique explicitly calculates the value of a cost function at candidate operating points and selects an operating point that moves the system repeatedly toward a lower cost. Another optimization technique uses a set of heuristic rules that substitute for complete models. In another optimization technique, a mathematical description of the cost function is analyzed to calculate the operating point that minimizes the function. As yet another optimization technique, energy consumption of the various physical components is physically measured at different operating points, and then optimization logic calculates the next operating point by comparing energy consumption at recent operating points. Identifying and using the operating state that minimizes energy use, while satisfying other goals, is valuable, but difficult and often overly complex.